Preliminary study on zeolite 13X as a potential carrier for algal immobilization

Immobilization of microalgae in polymers can overcome problems associated with biomass harvesting from suspended free cells cultivated in wastewater. Although various carriers have been applied for microalgae immobilization (e.g. natural such as alginate and synthetic such as polyacrylamide), problems such as low stability, toxicity and high cost still remain a challenge for the method to be commercialized. In the present study, an effective carrier (zeolite molecular sieves 13X) has been used for the immobilization of green microalgae, Chlorella vulgaris. The immobilization was done by suspending microalgae in a culture medium with different pHs (ranging from 5-9) along with zeolite 13X. Scanning electron microscope (SEM) was used to observe the morphology of the cells adsorbed onto the carrier after the immobilization process. It was found that higher microalgal immobilization occurred in the medium with an acidic condition (pH=5) compared to other pHs. This indicates that zeolite 13X is capable to be a potential support for the immobilization of Chlorella vulgaris. Furthermore, zeolite-immobilized Chlorella can be applied in different applications such as wastewater treatment and biofuel production

Stability improvement of algal-alginate beads by zeolite molecular sieves 13X

This research aimed to improve the stability of Chlorella-Alginate Beads (CABs) by zeolite molecular sieves 13X. Dissolution time of synthesized Zeolite-Algal-Alginate Beads (ZABs) in a chelating agent revealed a significant improvement on the beads stability (78.5 ± 0.5 min) compared to the control beads (51.5 ± 0.5 min) under the optimum conditions of zeolite/alginate (1.5:1), pH 5 and 2% of beads. Monitoring cell growth during 5 days of incubation showed good biocompatibility of zeolite 13X. Scanning electron microscopy (SEM) indicated rough surface and spherical shapes of ZABs. Energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) of ZABs confirmed the presence of zeolite 13X within the matrix. The zeta potential value of ZABs indicated that the beads were relatively stable. The findings of this research showed that zeolite molecular sieves 13X have the potential to improve the stability of algal-alginate beads compared to common beads

Kinetic and equilibrium modeling for the biosorption of metal ion by Zeolite 13X-Algal-Alginate Beads (ZABs)

The potential application of Zeolite 13X-Algal-Alginate Beads (ZABs) for copper biosorption was evaluated and compared with Blank-Alginate Beads (BABs) and Chlorella-Alginate Beads (CABs). Different process parameters were investigated including contact time, pH and initial metallic ion concentration. The findings indicated that the maximum biosorption capacity of ZABs was 85.88 mg/g biosorbent achieved at 180 min, pH 5 and initial metallic ion concentration of 150 mg/l whereas the maximum capacity of 70.02 and 77.32 mg/g biosorbent was obtained for BABs and CABs, respectively. ZABs showed higher stability than BABs and CABs in biosorption-desorption cycles. The kinetic and equilibrium data were analyzed via reaction/diffusion and Langmuir/Freundlich models, respectively. Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) indicated bonded metal ion to the ABs. Hence, this study confirmed an improvement in stability and biosorption capacity of microalgal-alginate beads

Improvement of algal-alginate bead stability by zeolite molecular sieves 13X and its application in biosorption

The interest in utilizing algae for wastewater treatment has been increased due to many advantages. Algae-Wastewater treatment system offers a cost-efficient and environmentally friendly alternative to conventional treatment processes. However, the recovery of free suspended algae from the treated effluent is one of the challenges during the treatment process. Therefore, the application of immobilized algae is a good approach to resolve the harvesting issue. Up to now, most of the algal immobilization has been done using cell entrapment method in which alginate (a natural polymer) has been applied as a carrier. Although alginate provides advantages in terms of biocompatibility, nontoxicity, cost-effectiveness, etc., this material has low stability to the chelating agents and a similar charge with cell surface of microorganisms, hence, it easily contributes to the leakage of large molecules due to the open lattice structure. Therefore, this study aims to improve the stability of Chlorella-Alginate Beads (CABs) by zeolite molecular sieves 13X (an aluminosilicate mineral with sodium ion) and further examined the potential use of the synthesized Zeolite 13X-Algal-Alginate Beads (ZABs) for copper biosorption from aqueous solution. The immobilization was done via the entrapment of green living microalgae, Chlorella vulgaris within alginate/powdered zeolite 13X hydrogels. Cross-linking was carried out using 0.1 M CaCl2 solution. The stability of the beads was tested by immersing them in a phosphate buffer solution at pH 7 as a chelating agent. Different process variables, including ratio of zeolite/alginate, pH and volume of beads were optimized using response surface methodology (RSM) to obtain the algal beads with high stability. Dissolution time of synthesized Zeolite-Algal-Alginate Beads (ZABs) in a chelating agent revealed a significant improvement on the beads stability (78.5 ± 0.5 min) compared to the control beads (51.5 ± 0.5 min) under the optimum conditions of zeolite/alginate (1.5:1), pH 5 and 2% of beads. Monitoring cell growth during 5 days of incubation showed good biocompatibility of zeolite 13X. Scanning electron microscopy (SEM) indicated rough surface and spherical shapes of ZABs. Brunauer-Emmett-Teller (BET) analysis revealed higher surface area for ZABs than other ABs. Energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) of ZABs confirmed the presence of zeolite 13X within the matrix. The zeta potential value of ZABs (−23.33 ± 0.29 mV) indicated that the beads were relatively stable. In addition, the potential use of ZABs for copper biosorption was evaluated and compared with Blank-Alginate Beads (BABs) and Chlorella-Alginate Beads (CABs). Different process parameters were investigated including contact time, pH and initial metallic ion concentration. It was found that the maximum biosorption capacity of ZABs was 85.88 mg/g biosorbent achieved at 180 min, pH 5 and initial metallic ion concentration of 150 mg/l whereas the maximum biosorption capacity of 70.02 and 77.32 mg/g biosorbent was obtained for BABs and CABs, respectively. ZABs showed higher stability than BABs and CABs in biosorption-desorption cycles. The kinetic and equilibrium data were analyzed via reaction/diffusion and Langmuir/Freundlich models, respectively. Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) analyses revealed bonded metal ion to the ABs. The findings of this research confirmed that modification of algal-alginate beads by zeolite molecular sieves 13X has the potential to improve the beads stability and their biosorption capacity

Potential of Zeolite and Algae in Biomass Immobilization

The interest in utilizing algae for wastewater treatment has been increased due to many advantages. Algae-wastewater treatment system offers a cost-efficient and environmentally friendly alternative to conventional treatment processes such as electrocoagulation and flocculation. In this biosystem, algae can assimilate nutrients in the wastewater for their growth and simultaneously capture the carbon dioxide from the atmosphere during photosynthesis resulting in a decrease in the greenhouse gaseousness. Furthermore, the algal biomass obtained from the treatment process could be further converted to produce high value-added products. However, the recovery of free suspended algae from the treated effluent is one of the most important challenges during the treatment process as the current methods such as centrifugation and filtration are faced with the high cost. Immobilization of algae is a suitable approach to overcome the harvesting issue. However, there are some drawbacks with the common immobilization carriers such as alginate and polyacrylamide related to low stability and toxicity, respectively. Hence, it is necessary to apply a new carrier without the mentioned problems. One of the carriers that can be a suitable candidate for the immobilization is zeolite. To date, various types of zeolite have been used for the immobilization of cells of bacteria and yeast. If there is any possibility to apply them for the immobilization of algae, it needs to be considered in further studies. This article reviews cell immobilization technique, biomass immobilization onto zeolites, and algal immobilization with their applications. Furthermore, the potential application of zeolite as an ideal carrier for algal immobilization has been discussed